The long term objective of the proposed research is to decipher the means by which the organism-environment interaction is relevant to the etiology of primary hypertension. The research strategy is prospective and focuses on blood pressure (BP) control in young adult humans when influenced by stressful events. Objectives of the proposed research primarily involve the use of field studies to evaluate BP and heart rate (HR) during naturalistic stressors. Previous laboratory studies have identified a subgroup of individuals who may be at risk for hypertension. These risks include myocardial and BP hyperreactivity to laboratory stressors mediated by increased beta-adrenergic activation particularly under conditions requiring active coping. Also, laboratory evoked myocardial hyperresponsivity is disproportionately greater than any increase in O2 consumption and in certain individuals is associated with sodium retention, events which can influence BP control. The proposed field studies serve two purposes. One, they permit an evaluation of the extent laboratory reactivity generalizes to real life stressors. This phase of the field studies would use study subjects in whom an extensive laboratory hemodynamic evaluation has been recently obtained and within the environment of the University community which provides a reasonably uniform variety of stressors. A second purpose will be to determine whether there is any relationship to reactivity observed under laboratory conditions 10 years ago to existing levels and reactivity of BP and HR in the working and home environment, assessing the impact of individual copying styles and other psychosocial influences. For both types of field studies, an ambulatory, automated monitoring system has been developed which provides accurate measures of BP and HR.